Air pollution levels vary greatly between different places, and one might wonder, if a city planted more trees, would it help clean the air?
Findings from a study led by researchers at the University of Gothenburg in Sweden have concluded that, yes, trees contribute to cleaner air in cities.
The study was conducted on seven urban settings in Gothenburg using the sample leaves of a pin oak tree, deciduous tree, and even a conifer, a black pine. It showed that while the pollutants in the leaves increased over time, the levels of pollutants in the air decreased, showing a clear correlation between the level of clean air and the concentration of pollutants absorbed by the leaves.
“The study establishes that the leaves collect the air pollutants during the summer, thus reducing human exposure to harmful substances in the air,” says Håkan Pleijel, researcher and professor of environmental sciences at the University of Gothenburg University.
“These types of extensive measurements of pollutants in both vegetation and the air are unusual, and the study confirms that trees play a role in improving air quality in cities.”
At the same time, the researchers found that pollution levels were higher in areas where there are fewer trees in the city. For example, Nils Ericsson Terminal, a bus station, has higher pollutants than Angered City Park.
A surprising discovery: conifers – trees with cones instead of leaves – was proved to be as important in the cleansing of city air. The study found that the levels of pollutants in needles in a three-year-old black pine were considerably higher when compared to one-year-old needles.
“An advantage with conifers is that the needles remain on the trees even in the winter when pollution levels in cities are often at their highest,” said Jenny Klingberg, a researcher in environmental sciences at Gothenburg Botanical Garden.
The researchers hope that their study will be used on urban planning and city development.
“We need to work with multiple methods to reduce air pollution levels in our increasingly tightly populated cities. Of course, reducing emissions is the most important measure, but we show that vegetation also plays an important role in creating sustainable cities where residents are healthy,” Klingberg added.